1. Field of the Invention
The present invention relates to an apparatus and method used in an electrical die sorting (EDS) process of a semiconductor test process, and more particularly, to a probe card that transmits an electrical signal for testing a chip to a chip pad on a wafer, a test apparatus having the probe card, and a test method using the test apparatus.
2. Description of Related Art
Generally, a semiconductor manufacturing process includes a fabrication process for forming a plurality of chips on a wafer, an EDS process for testing electrical characteristics of each chip formed on the wafer, and an assembly process for individually separating good chips tested by the EDS process and packaging the chips to prevent the chips from mechanical, physical, and chemical impact from the exterior.
The EDS process is a process of determining whether each chip formed on the wafer is good or bad by transmitting a predetermined electrical signal to each chip on the wafer and then checking a signal received in response to the transmitted electrical signal.
However, since each chip formed on the wafer has a very small size, it is very difficult to directly connect a tester for applying a predetermined electrical signal to each chip. Therefore, a probe card is used as an intermediate device, and the probe card having a plurality of probe needles is disposed between the tester for generating the predetermined electrical signal and the wafer at which the chips are formed. The tester generates a predetermined electrical signal for testing the chip to transmit the signal to the probe card, and the probe card transmits the electrical signal to each chip through the probe needles. As a result, whether each chip is good or bad is determined by comparing the transmitted signal and a signal checked from the transmitted signal.
The wafer tested by the EDS process is subjected to a high temperature of about 80˜100° C. during the process. This is because it is possible to increase the operational reliability of the wafer by testing the chip at high temperature.
However, in this case, the probe needles contacting the chip on the wafer are also heated to the high temperature, which to causes various problems.
First, the probe needles heated to the high temperature may be deformed, i.e., twisted, bent or the like. In this case, since the probe needles may not be in contact with a terminal of the chip, i.e., a pad of the chip, with which the probe needles should be contacted, a good chip may be mistaken as a bad chip.
Second, the probe needles heated to the high temperature may be more readily stained with impurities in comparison with the probe needles at a low temperature. In this case, the probe needles may also mistake a good chip stained with the impurities as a bad chip. Therefore, after contacting a certain number of chips, the probe needles are sanded by a surface having a predetermined roughness such as sand paper to remove the impurities stuck to an end of the needle. However, since the end of the needle may be more readily stained with the impurities due to the high temperature, the sanding time is increased, thereby significantly reducing the number of chips that can be tested per unit time.